“If by whiskey you mean the water of life that cheers men’s souls, that smoothes out the tensions of the day, that gives gentle perspective to one’s view of life, then put my name on the list of the fervent wets.

But if by whiskey you mean the devil’s brew that rends families, destroys careers and ruins one’s ability to work, then count me in the ranks of the dries."

If true, this is quite contrary to the advice in Warren's own book, How To Win In Politics, where he favors candidates "taking a positive and unequisition on all pertinent issues." (Yes, I know it's probably supposed to be "unequivocalposition," but the single source I have for the quote gives it as above.)

On the other hand, other sources have the text of a similar speech was given by Judge Noah "Soggy" Sweat Jr., a
former Mississippi legislator, in 1952 during his last year in office:

My friends, I had not intended to discuss this controversial subject at this particular time. However, I want you to know that I do not shun controversy. On the contrary, I will take a stand on any issue at any time, regardless of how fraught with controversy it might be. You have asked me how I feel about whiskey. All right, here is how I feel about whiskey.

But if, when you say whiskey, you mean the oil of conversation, the philosophic wine, the ale that is consumed when good fellows get together, that puts a song in their hearts and laughter on their lips and the warm glow of contentment in their eyes; if you mean Christmas cheer; if you mean the stimulating drink that puts the spring in the old gentleman's step on a frosty, crispy morning; if you mean the drink which enables a man to magnify his joy and his happiness and to forget, if only for a little while, life's great tragedies and heartaches and sorrows; if you mean that drink the sale of which pours into our treasuries untold millions of dollars which are used to provide tender care for our little crippled children, our blind, our deaf, our pitiful aged and infirm, to build highways and hospitals and schools, then I certainly am for it.

Although Sweat's speech does not use the exact phrase "if-by-whiskey," it's a lot better documented than Warren's remarks. (A lone site claims the origin of the phrase is with an unnamed Kentucky congressman.)